1、Designation: D2896 11Designation: 276/95Standard Test Method forBase Number of Petroleum Products by PotentiometricPerchloric Acid Titration1This standard is issued under the fixed designation D2896; the number immediately following the designation indicates the year oforiginal adoption or, in the c
2、ase of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This te
3、st method covers the determination of basicconstituents in petroleum products by titration with perchloricacid in glacial acetic acid.1.2 Procedures A and B use different titration solventvolumes and sample weights.NOTE 1A round robin on a series of new and used oils and additiveconcentrates has sho
4、wn that the two procedures give statistically equiva-lent results.1.3 Appendix X2 provides the use of an alternative solventsystem which eliminates the use of chlorobenzene in this testmethod. The use of the alternative solvent gives statisticallyequivalent results; however, the precision is worse.
5、ParagraphX2.5.5 provides guidance when comparing results using thetwo different solvents.1.4 The constituents that may be considered to have basiccharacteristics include organic and inorganic bases, aminocompounds, salts of weak acids (soaps), basic salts of poly-acidic bases, and salts of heavy met
6、als.NOTE 2This test method is applicable to both fresh oils and used oilsas described in Sections 16, 17, and 19 and Appendix X1.1.5 This test method can be used to determine base number300 mg KOH/g. However, the precision statement in Section19 has been obtained only on base number #300 mg KOH/g.1.
7、6 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-
8、priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specificwarning statements, see Section 7, Section 10, and X2.2.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent Water3. Terminology3.1 Definitions:3.1.1 base num
9、berthe quantity of a specified acid, ex-pressed in terms of the equivalent number of milligrams ofpotassium hydroxide per gram of sample, required to titrate asample in a specified solvent to a specified endpoint using aspecified detection system.4. Summary of Test Method4.1 The sample is dissolved
10、in an essentially anhydrousmixture of chlorobenzene and glacial acetic acid and titratedwith a solution of perchloric acid in glacial acetic acid usingpotentiometric titrimeter. A glass indicating electrode and areference electrode are used, the latter being connected withthe sample solution by mean
11、s of a salt bridge. The meterreadings are plotted against the respective volumes of titratingsolution, and the end point is taken at the inflection in theresulting curve.4.2 ProcedureAuses 120 mL of titration solvent. ProcedureB uses 60 mL of titration solvent. In addition, the twoprocedures use dif
12、ferent equations for the calculation of appro-priate sample weights. Since many portions of the test methodare identical for Procedures A and B, only the unique sectionswill be described separately for the two versions of the testmethod.1This test method is under the jurisdiction of ASTM Committee D
13、02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.06 on Analysis of Lubricants.Current edition approved May 15, 2011. Published July 2011. Originallyapproved in 1970. Last previous edition approved in 2007 as D289607a. DOI:10.1520/D2896-11.This test method ha
14、s been approved by the sponsoring committees and acceptedby the cooperating societies in accordance with established procedures.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informatio
15、n, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.3 Occasionally certain used oils give no inflectio
16、n in theforward titration mode, in which case a back titration modifi-cation with sodium acetate titrant is employed.5. Significance and Use5.1 New and used petroleum products can contain basicconstituents that are present as additives. The relative amountsof these materials can be determined by tit
17、ration with acids.The base number is a measure of the amount of basic substancein the oil, always under the conditions of the test. It issometimes used as a measure of lubricant degradation inservice; however, any condemning limits must be empiricallyestablished.6. Apparatus6.1 Potentiometric Titrim
18、eters, either automatic recordingor manual.6.2 Glass Electrode, pH 0 to 11, general-purpose type.6.3 Reference Electrode, silver/silver chloride (Ag/AgCl)reference electrode with a nonaqueous bridge as described inSection 10. (See also 19.1.)NOTE 3Some reference electrodes with fritted or fiber diap
19、hragmsand some combined glass plus reference electrodes systems are commer-cially available, such as the single-rod glass plus silver/silver chlorideelectrode assembly. During the development of this test method, the use ofelectrodes of these types gave problems in some laboratories, but not inother
20、s. Accordingly, these electrodes are permitted in this test method,provided that the sodium perchlorate bridge is used; however, whenstability or other problems arise with their use, the sleeve-type electrodeshould be used.6.4 Stirrer, either mechanical or electrical, with variablespeeds and with pr
21、opeller or paddle of chemically inertmaterial. When an electrical stirrer is used, it must be groundedso that disconnecting or connecting the power to the motor willnot produce a permanent change in meter reading during thecourse of a titration. A magnetic stirrer with stirring bar can beused provid
22、ed it meets these conditions.6.5 Buret, 10 or 20-mL, graduated in 0.05-mL divisions andcalibrated with an accuracy of 60.02 mL, or an automaticburet of similar accuracy.6.6 Titration Beaker, made of borosilicate glass or othersuitable titration beaker, tall form recommended.6.6.1 For Procedure A, us
23、e a beaker of 250 or 300 mLcapacity. For Procedure B, use a beaker of about 150 mLcapacity such that 60 mL of titration solvent will cover theelectrodes.NOTE 4Other beakers of suitable size capacity may be used.6.7 Titration Stand, suitable to support the beaker, elec-trodes, stirrer, and buret. An
24、arrangement that allows for theremoval of the beaker without disturbing the electrodes, buret,and stirrer is desirable.NOTE 5Some apparatus may be sensitive to interference by staticelectricity, shown by erratic movements of recorder pen or meter indicator,when the titration assembly (beaker and ele
25、ctrodes) is approached by theoperator. In this case surround the beaker closely with a cylinder of coppergauze that is electrically grounded.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents s
26、hall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccura
27、cy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water that meetsthe requirement of either Type I, II, or III of SpecificationD1193.7.3 Acetic Acid, glacial (WarningToxic and irritant).7.4 Acetic Anhydride (WarningToxic and
28、 irritant).7.5 Chlorobenzene (WarningToxic and irritant).7.6 Perchloric Acid, Standard Solution in AceticAcid (0.1 N)4(WarningPowerful oxidant when dry orheated. Great care should be taken to avoid contact withorganic matter under conditions that may result in subsequentdrying or heating, and spills
29、 should be washed immediatelyand thoroughly with water)Mix 8.5 mL of 70 to 72 %perchloric acid (HClO4,70to72%)(or10.2 mL of 60 to 62 %HClO4solution) with 500 mL of glacial acetic and 30 mL (or35 mL if the 60 to 62 % HClO4solution is used) of aceticanhydride. Dilute to 1 L with glacial acetic acid. A
30、llow thesolution to stand for 24 h.NOTE 6Excess acetic anhydride should be avoided to prevent acety-lation of any primary or secondary amines that may be present.7.7 Potassium Hydrogen Phthalate(KHC8H4O4).7.8 Sodium Perchlorate Electrolyte(WarningSodiumperchlorate is toxic and an irritant. It is als
31、o a powerfuloxidizing agent when heated. Great care should be taken toavoid contact with organic matter under conditions that mayresult in subsequent drying or heating, and spills should bewashed immediately and thoroughly with water.) Prepare asaturated solution of sodium perchlorate (NaClO4) in gl
32、acialacetic acid. An excess of undissolved NaClO4shall always bepresent at the bottom of the solution.7.9 Titration SolventAdd one volume of glacial aceticacid to two volumes of chlorobenzene.7.10 Sodium Carbonate, anhydrous (Na2CO3).7.11 Sodium Acetate Solution, 0.1 N in acetic acid (for backtitrat
33、ion, see Sections 16 and 17)Dissolve 5.3 g of anhydrousNa2CO3in 300 mL of glacial acetic acid. Dilute to 1 L withacetic acid after solution is complete.8. Standardization of Reagents8.1 Perchloric Acid SolutionThe standardization of theperchloric acid solution (HClO4) differs for the two proceduresa
34、s follows:3Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States
35、 Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.4Available commercially for purchase already prepared.D2896 1128.1.1 Procedure A (120 mL)Heat a quantity of potassiumhydrogen phthalate in an oven at 120C for 2 h and allow it tocool. Take 0.1 to 0.2 g of t
36、he potassium hydrogen phthalateweighed to the nearest 0.1 mg and dissolve it in 40 mLof warmglacial acetic acid. Add 80 mL of chlorobenzene, cool, andtitrate with 0.1 N HClO4solution, using the electrode systemand procedures given in 10.1 to 10.4 and 11.4 to 11.7. Detectthe end point by the same pro
37、cedure used for base numberdetermination (see 14.2). Carry out a blank titration on 40 mLof glacial acetic acid plus 80 mL of chlorobenzene (see 11.8).8.1.2 Procedure B (60 mL)Heat a quantity of potassiumhydrogen phthalate in an oven at 120C for 2 h and allow it tocool. Take 0.05 to 0.1 g of the pot
38、assium hydrogen phthalateweighed to the nearest 0.1 mg and dissolve it in 20 mLof warmglacial acetic acid. Add 40 mL of chlorobenzene, cool, andtitrate with 0.1 N HClO4solution as described in 8.1.1. Carryout a blank titration on 20 mL of glacial acetic acid and 40 mLof chlorobenzene (see 11.8).8.1.
39、3 Calculate the normality, NA, of the HClO4solution asfollows:NA5 1000W/204.23V b!# (1)where:W = potassium hydrogen phthalate, g,V = HClO4solution used, mL, andb = volume corresponding to V for the blank titration,mL.NOTE 7Because of the relatively large coefficient of volumetricexpansion of organic
40、 liquids, the acetous HClO4solution should be usedwithin 6 5C of the temperature at which it was standardized. If used ata temperature more than 5C higher, multiply the volume used by thefactor 1 (t0.001). If used at a temperature more than 5C lower,multiply by the factor 1 + (t0.001), where tis the
41、 difference in degreesCelsius between temperatures of standardization and use and is alwayspositive.8.2 Sodium Acetate SolutionThe standardization of thesodium acetate solution (Na2CO3) differs for the two proce-dures as follows:8.2.1 Procedure A (120 mL)Use 120 mL of titrationsolvent and 8.00 mLof
42、0.1 NHClO4solution.Titrate with 0.1 Nsodium acetate solution, using the electrode system and pro-cedure given in 10.1 to 10.4 and 11.4 to 11.7. Detect the endpoint by the same procedure as will be used for base numberdetermination (see 14.2). Calculate the normality, NB,ofthesodium acetate solution
43、as follows:NB5 8.00 b!NA#/G (2)where:b = volume corresponding to V for the blank titration,NA= normality of the HClO4solution, andG = volume of standard sodium acetate used in thestandardization, mL.8.2.2 Procedure B (60 mL)Use 60 mL of titration solventand 4.00 mL of 0.1 N HClO4solution. Titrate as
44、 described in8.2.1. Calculate the normality, NB, of the sodium acetatesolution as follows:NB5 4.00 b!NA#/G (3)where:b = volume corresponding to V for the blank titration,NA= normality of the HClO4solution, andG = volume of standard acetous sodium acetate used inthe standardization, mL.9. Preparation
45、 of Sample9.1 It is essential to ensure that the sample is representativesince any sediment can be acidic or basic or have adsorbedacidic or basic material from the sample. When necessary,samples are warmed to aid mixing. Used oils should bevigorously shaken to ensure homogeneity before sampling.NOT
46、E 8As used oils can change appreciably in storage, samplesshould be tested as soon as possible after removal from the lubricatingsystem and the dates of sampling and testing, if known, should be noted.10. Preparation of Electrode System10.1 Preparation of ElectrodesWhen the reference elec-trode is t
47、o be changed from aqueous bridge to nonaqueous,drain out the aqueous solution, wash out all crystals of KClwith water, then rinse the outer jacket (salt bridge) severaltimes with NaClO4electrolyte solution. Finally fill the outerjacket with NaClO4electrolyte solution up to the filling hole.When usin
48、g the sleeve-type electrode, carefully remove theground-glass sleeve and thoroughly wipe both ground surfaces.Replace the sleeve loosely and allow a few drops of electrolyteto drain through to flush the ground-glass joint and to wet theground surfaces thoroughly with electrolyte. Set the sleevefirml
49、y in place, refill the outer jacket with the NaClO4electrolyte solution, and rinse the electrode with chloroben-zene. When in use, the electrolyte level in the referenceelectrode should be kept above that of the liquid in the titrationbeaker to prevent entry of contaminants into the salt bridge.When not in use, fill the reference electrode with the NaClO4electrolyte solution, leave the bung in the filling orifice, andimmerse both electrodes in distilled water, keeping the level ofthe electrolyte above that of the distilled water.10.2 T
